DE 10 2011 051 931 A1 describes an OLED coating device. In a deposition reactor, a susceptor is situated, the surface of which is cooled and carries a substrate which is to be coated. A carrier gas-vapor mixture is fed into the process chamber from a gas inlet member which is heated to a temperature above the condensation temperature of a vapor. The vapor condenses on the surface of the substrate, wherein the quality of the layer depends on the one hand on the concentration (the partial pressure) of the vapor in the process chamber, but on the other hand also on the temperature of the substrate surface. In a method for separating OLED layers on a substrate, the maintaining of a temporally constant vapor flow rate into the process chamber is desired. The vapor is generated in a vapor generator by the application of heat on a solid or liquid starting material. The starting material can be brought as an aerosol into a vaporization volume. The vaporization volume is flowed through by a carrier gas, with which the vapor is brought into the process chamber. The carrier gas is fed via a mass flow controller into the pipeline system of the vaporization device. With a second sensor, a sensor signal is obtained, which is influenced by the concentration (the partial pressure) of the vapor.
From WO 2010/130775 A1, US 2006/0179918 A1 and U.S. Pat. No. 8,215,171 B1 so-called QCM sensors (quartz crystal microbalance) are known. These sensors are used in vacuum vaporization devices, so-called VTE systems (vacuum thermal evaporation). A QCM sensor consists of a quartz crystal, which is stimulated to oscillate in its resonance frequency. In the vaporization, for example the vaporization of objects with metals, for example gold, or else also in the vaporization of objects with non-metals, a certain amount of vapor condenses on a portion of the surface of the oscillating body formed by the quartz. In the prior art, the oscillating body is kept at a temperature of approximately 50° C. During the coating process, a condensate layer grows on the surface of the oscillating body. This additional mass detunes the oscillating body, so that the frequency changes temporally. This takes place according to the so-called SAUERBREY equation. In the known use of this QCM sensor, the coating process is terminated when this oscillation frequency has reached a predetermined final value.
After a specified number of coating processes, the sensor must either be exchanged or cleaned, so that its oscillating capability is maintained, because the layers which are deposited on the quartz crystal influence not only the frequency, but also the amplitude, because they act in a damping manner.
Due to the type of construction, commercially available QCM sensors can not be used at high temperatures lying substantially above 50° C.